Knee arthroplasty prosthesis and method

ABSTRACT

A knee arthroplasty prosthesis includes a femoral component having multiple pieces with engagement means provided for engaging various pieces of the femoral component to one another following their insertion in the incised area of the femur. A tibial component includes multiple pieces designed for assembly following positioning in the incision. The tibial component includes a Morse taper cavity on one piece of the tibial component and a Morse taper extension on another member of the component for receipt therein.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims priority under U.S.Provisional Application Ser. No. 60/358,174 filed Feb. 20, 2002.

BACKGROUND OF THE INVENTION

In performing knee arthroplasty with conventional knee prostheses, ithas been necessary to form large incisions in order to accommodate thepreparation of the femur to receive the prosthesis and to accommodatethe reception of a fairly large prosthesis into the incised femur forimplantation on the prepared distal end of the femur. As is appreciatedby those skilled in the art, it is desirable to minimize the size of anyincision as the smaller the incision, the more rapidly the patient mayrecover. Prior art prostheses formed with a single piece metal componenthaving both left and right condylar portions integral with the patellarflange area require large incisions in order to accommodate implantationin the prepared femur. In contrast, under the present invention, throughthe use of multiple pieces for the femoral component, it is possible togreatly reduce the size of any such incision, thereby reducing theamount of damage to soft tissue from any such arthroplasty and speedingthe time of recovery. Similarly, it is desirable to minimize the size ofany incision in the tibia during any implantation of the tibialcomponent.

SUMMARY OF THE INVENTION

The present invention is directed to a prosthesis for use in kneearthroplasty including total knee arthroplasty which is minimallyinvasive to the patient and to a method for performing surgery usingsuch prosthesis including the femoral and tibial components thereof.Under the invention, the femoral component and, preferably, the tibialcomponent are manufactured in at least two and possibly three or morepieces. However, it is possible that the tibial component could be asingle piece, monoblock construction as well as modular multipiececonstruction. In both the single piece and multipiece construction,there is also provided a plastic articular surface insert piece. Thepieces are designed to be assembled together following insertion intothe knee. This allows total knee arthroplasty to be performed throughvery small incisions, as small as three inches, in each of the distalend of the femur and proximal end of the tibia. Following insertion, thepieces of the femoral component implanted at the distal end of the femurare joined together with a locking mechanism to form the modular femoralcomponent and the pieces of the tibial component implanted at theproximal end of the tibia are assembled to form the modular tibialcomponent.

Femoral Component

The femoral component may have three component pieces for a cruciateretaining design and two component pieces for a cruciate sacrificingdesign. It may be manufactured as two or three separate pieces ormanufactured as a single unitary member which is subsequently cut orotherwise divided into two or three separate pieces. The pieces areprovided with a locking joint for retaining the pieces togetherfollowing insertion in distal end of the femur. The locking joint forthe pieces is placed at the area of low patella/femoral contact, a lowstress area of the femur. This corresponds to the anterior chamfer cutof a routine total knee arthroplasty and the area can be easilyreinforced to accommodate the additional thickness of the locking joint.Various locking mechanisms may be employed for joining the piecestogether including screws or a transverse locking pin which may beinserted from the medial side and/or lateral side. The lockingmechanisms of whatever type lock the component pieces together into asolid assembled prosthesis. The prosthesis will be additionallyreinforced by the underlying bone and/or cement fixation and willproduce a durable construction. The patellar flange and the area of anyjoint between assembled components which may be contacted by the patellashould be smoothed and, possibly, recessed to prevent premature wear ofthe patellar member as it tracks over the joint in the femoralcomponent.

Tibial Component

The tibial component preferably has two pieces, namely, a tibial baseand a tibial stem. It is also inserted in pieces from the side. It mayalso be a monoblock, one-piece tibial component with pegged or shortstem fixation. The tibial base may have of a flat baseplate withanterior and posterior dovetails and may have a tapered transverse keel.The other piece of the tibial component is a modular stem which isinserted from the top after the baseplate is inserted. This designallows the components to be inserted through the minimal incision andstill have long term stability. The stem is preferably fixed with areverse Morse taper so that it can be driven through the baseplate likea spike.

Patellar Component

A standard conforming dome configuration patellar component is utilized,with the main difference being its method of insertion. It may beinserted without everting the patella. This is accomplished with the useof special instrumentation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of femoral componentshowing the medial condyle as a separate piece from the remainder of thefemoral component.

FIG. 2 is a perspective view of a second embodiment of femoral componentshowing the lateral condyle as a separate piece from the remainder ofthe femoral component.

FIG. 2A is a sectional view showing a patellar member engaged to thearticulating surface of the patellar femoral flange piece.

FIG. 3 is a perspective view of another embodiment of femoral componentshowing both the medial condyle and the lateral condyle as separatepieces from the patellar femoral flange piece of the femoral component.

FIG. 4 is a perspective view showing the patellar femoral flange pieceof FIG. 3 taken from a different angle.

FIG. 5 is a perspective view of an embodiment of femoral componentshowing the patellar femoral flange piece as a separate piece from theremainder of the femoral component.

FIG. 6 is a front view of the embodiment of the femoral component ofFIG. 5.

FIG. 7 is a side view of the embodiment of the femoral component of FIG.5.

FIG. 8 is a sectional view taken through line 8-8 of FIG. 6.

FIG. 9 is a sectional view taken through line 9-9 of FIG. 6.

FIGS. 10 and 11 are perspective views of other embodiments of thefemoral component showing the patellar femoral flange piece as aseparate piece from the remainder of the femoral component.

FIG. 11A is a view similar to FIG. 9 for the embodiment of FIG. 11.

FIG. 11B is a sectional view through line 11B-11B of FIG. 11A.

FIG. 12 is a perspective view of another embodiment of femoral componentshowing the patellar femoral flange piece as a separate piece from theremainder of the femoral component and showing one form of design forconnecting the patellar femoral flange piece to the remainder of thefemoral component.

FIG. 13 is an enlarged view of the circled portion of FIG. 12.

FIG. 14 is a perspective view of an embodiment of femoral componentshowing the lateral condyle as a separate piece from the remainder ofthe femoral component.

FIG. 15 is an enlarged view of the circled portion of FIG. 14.

FIG. 16 is a perspective view of another embodiment of femoral componentshowing the patellar femoral flange piece as a separate place from theremainder of the femoral component.

FIG. 17 is an enlarged view of the circled portion of FIG. 16.

FIG. 18 is a perspective view of the tibial component showing the stemportion thereof as a separate piece from the base.

FIG. 18A is a view similar to FIG. 18 with the added feature of a stemextension as part of the tibial component.

FIG. 19 is a sectional view of another embodiment of tibial componentshowing the stem portion thereof as a separate piece from the base.

FIG. 20 is a perspective view of another embodiment of tibial componentshowing the stem portion thereof as a separate piece from the base.

FIG. 21 is a side view of the tibial component of FIG. 20 showing itsimplantation in the proximal end of a prepared tibia.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown one embodiment of femoral componentgenerally designated by the numeral 10. The femoral component includes afirst piece 12 having a patellar flange portion 14 and an integral,unitary lateral condyle portion 16 extending therefrom. A prior artfemoral component would also have an integral, unitary medial condyle onthe opposite side from the lateral condyle portion 16. Under the presentinvention, there is provided, as a separate piece, a medial condylepiece 18 intended to be assembled to the first piece 12 followingimplantation of both the first piece 12 and the medial condyle piece 18in the patient. The assembly mechanism or locking joint for securing themedial condyle piece 18 to the first piece 12 will be hereinafterdescribed.

As shown in FIG. 1, the medial condyle piece 18 is provided with arecess 15 for receiving bone cement and a pair of fixation pins 17. Thefirst piece 12 may also be provided with one or more recesses andfixation pins. If it is desired to have a prosthesis for implantationwithout bone cement, the recesses such as the recess 15 can be replacedby one of several types of porous surfaces well known in the art forbone in-growth.

Referring to FIG. 2, there is shown a second embodiment of a femoralcomponent 20 having a first piece 22 with a patellar femoral flangeportion 24 and an integral, unitary medial condyle portion 26. Thesecond component of this embodiment is a lateral condyle piece 28 whichmay be joined with the first piece 22 following implantation of both thefirst piece 22 and the lateral condyle piece 28 in the femur of thepatient.

FIG. 2A shows a sectional view of patellar member P in contact with thearticulating surface of the patellar femoral flange portion 24.

FIG. 3 shows yet another embodiment of a three-piece femoral component30. Under this embodiment, there is provided a patellar femoral flangepiece 32, a second piece 34 which is a medial condyle piece and a thirdpiece 36 which is a lateral condyle piece assuming, of course,implantation in the right knee of a patient. If the femoral component 30were implanted in the left knee of a patient, the second piece 34 wouldbe the lateral condyle piece and the third piece 36 would be the medialcondyle piece. Each of the second piece 34 and the third piece 36 arejoined to the patellar femoral flange piece 32 following insertion inthe patient's femur by use of a locking joint to be hereinafterdescribed.

All three of the pieces of the femoral component may be provided withfixation pins 37 and recesses 35 if intended for use with bone cement ora porous surface if intended for non-cemented implantation.

FIG. 4 is a perspective view of the patellar femoral flange piece ofFIG. 3 taken from a different angle.

The femoral components 10, 20 and 30 of FIGS. 1 through 3 could be usedfor implantation in either knee. The foregoing description for each ofthe femoral components 10, 20 and 30 is based on the assumption ofimplantation in the right knee. If they were used for implantation inthe left knee, the pieces identified by the numerals 18 and 34 would belateral condyle pieces, the pieces identified by the numerals 28 and 36would be medial condyle pieces, the portion identified by the numeral 16would be a medial condyle portion and the portion identified by thenumeral 26 would be a lateral condyle portion.

Referring to FIGS. 5, 6, 7, 8 and 9, there is shown an embodiment offemoral component 40 having two pieces, namely, a patellar femoralflange piece 41 and a condylar piece 42. The patellar femoral flangepiece 41 has a patellar engaging surface 43 shaped to allow anatomicaltracking of a natural or prosthetic patella P. As shown in FIG. 5, thepatellar femoral flange piece 41 has a superior bone engaging surface 46and a patellar engaging surface 43 defining a portion of an inferiorarticulating surface. The patellar femoral flange piece 41 extends froman inferior end 45 to a leading end 48 which is contoured to engage thecondylar piece 42. The condylar piece 42 includes a first condylarportion 50 and a second condylar portion 52 and extends from anengagement end 54 contoured to receive the leading end 48 of thepatellar flange 41 to a posterior end 55. As will be appreciated bythose skilled in the art, the femoral component 40 could be used forimplantation in either a right knee or left knee and the first andsecond condylar portions will be either lateral or medial facingdepending upon the knee in which the femoral component 40 is implanted.

The condylar piece 42 has a superior bone engaging surface with a seriesof bone engaging flats 60, 61, 62 and 63 disposed at varying anglesconsistent with cuts made in preparing the distal end of the femur toreceive the condylar piece 42. If desired, the superior bone engagingsurface 46 of the patellar flange piece 41 and the superior boneengaging surfaces 60, 61, 62 and 63 of the condylar piece 42 may beformed with recesses for receiving bone cement or porous surfaces forbone ingrowth and may also be provided with fixation pins.

The condylar piece 42 in the embodiment of FIGS. 5-9 is formed as asingle unitary piece for implantation. As such, the first condylarportion 50 and the second condylar portion 52 are joined together with aposterior cam 56 which may be formed integral with or welded orotherwise joined to the first and second condylar portions 50, 52. Theengagement end 54 of the condylar piece 42 also has the first and secondcondylar portions 50, 52 joined together by a laterally extending crossmember 57. As will be appreciated by those skilled in the art, the useof the posterior cam 56 will result in sacrificing of the posteriorcruciate ligament. As will be appreciated, in those cases where it maybe necessary to sacrifice the posterior cruciate ligament for otherreasons, the feature of having both a posterior cam 56 and a crossmember 57 for joining the first and second condylar pieces 50, 52 willprovide great rigidity to the condylar piece 42.

As can be seen in FIGS. 5, 7 and 9, the cross member 57 has a superiorbone engaging surface 57A and a medial surface 57B approximately midwaybetween the superior bone engaging surface 57A and the articulatingsurfaces 51 and 53 of the first condylar portion 50 and second condylarportion 52, respectively. On the posterior side of the cross member 57is a posterior wall surface 57C extending between the superior boneengaging surface 57A and the surface 57B. Opposite the posterior surface57C is a fourth surface 57D which will engage a corresponding surface tobe described of the patellar femoral flange piece 41.

The engagement ends 54 for each of the first and second condylarportions 50, 52 each follows a curved path defined by sidewallengagement surface 54A as shown in FIGS. 5 and 6. Each of the curvedengagement wall surfaces 54A extends to the general area defined by theposterior wall surface 57C of cross member 57. (See FIG. 5). Thepositioning of the joint defined by the surfaces 54A of the condylarpiece 42 and the mating surfaces of the patellar femoral flange piece 41is important and should be in the vicinity of the normal femoral tidemark which is a low stress area of contact by sliding engagement of thepatella. By providing the joint in this area, the prosthesis has greatability to function as desired with no separation of the patellarfemoral flange piece 41 from the condylar piece 42 followingimplantation. The normal femoral tide mark corresponds to the area ofthe inferior chamfer cut of a routine total knee arthroplasty.

The patellar femoral flange piece leading end 48 has a pair of curvedengagement surfaces 64 following a contour for mating engagement withthe respective surfaces 54A of the condylar piece 42. Centrallypositioned between the curved engagement surfaces 64 is a central wallsurface 65 which, when the patellar femoral flange piece 41 is engagedto the condylar piece 42, lies in substantially the same plane as thesurface 57C of cross member 57. (See FIG. 9). The central wall surface65 extends superiorly from the patellar engaging surface 43 to a ledge66 intended to rest upon the surface 57B of cross member 57. The ledge66 extends away from the central wall surface 65 to a central engagementsurface 67 which is intended to engage the surface 57D of cross member57. A bone engaging surface 68 extends from the central engagementsurface 67 toward the anterior end 45.

As shown in FIGS. 6, 7 and 9, the condylar piece 42 may be secured tothe patellar femoral flange piece 41 by means of screws 68 extendingthrough apertures 69 extending through engagement end area 54 of therespective first and second condylar portions 50 and 52, through theengagement end surfaces 54A and into aligned threaded apertures 71extending inwardly from the curved engagement surfaces 64 of thepatellar femoral flange piece 41.

Referring to FIG. 8, there is shown the articulating surface defined bythe patellar engaging surface 43 of the patellar femoral flange piece 41and the articulating surface 59 of the condylar piece 42 in the area ofthe joint defined by the mating surface 54A of the condylar piece 42 andsurface 64 of the patellar femoral flange piece 41. As can be seen inFIG. 8, the respective surfaces 43 and 59 are recessed slightly at suchjoint to provide a slight dip 73 so that any movement of the patellarmember P over such joint will leave a slight gap between the surface ofthe patellar member P and the surfaces 43 and 59 at the dip 73.

The presence of the gap and the dip 73 has a two-fold advantage. Itreduces the amount of stress in that area of the joint defined by themating surfaces 54A and 64 at the surfaces 43 and 59. Additionally, ifthere is a slight mismating of the patellar femoral flange piece 41relative to the condylar piece 42 such that one of the surfaces 43 or 59were slightly high or lower than intended for precise fixation, thepresence of the dip 73 will serve to prevent the patellar member P fromcontacting and being subjected to premature wear by a sharp corner ofthe higher piece.

Referring to FIG. 10, there is shown a further embodiment similar tothat of FIGS. 5 through 9 but one in which there is provided a condylarpiece 42A having the first condylar portion 50A is joined to the secondcondylar portion 52A only by a posterior cam 56A. Under this embodiment,the patellar femoral flange piece 41A has a central wall surface 65Acentrally positioned between curved engagement surfaces 64A. The centralwall surface 65A extends throughout the thickness of the patellarfemoral flange piece 41A. Therefore, there is no ledge similar to theledge 66 shown in FIG. 5. All other features of the embodiment of FIG.10 are similar to corresponding features of the embodiment of FIGS. 5,6, 7, 8 and 9.

Referring to FIGS. 11, 11A and 11B, there is shown a further embodimentof femoral component 40B similar to that of FIGS. 5 through 9 but one inwhich there is provided a condylar piece 42B having the first condylarportion 50B joined to the second condylar portion 52B only by a crossmember 57B and a modified connector means for fastening the condylarpiece 42B to the patellar femoral flange piece 41B.

The cross member 57B is provided with an extension 130 extendingsuperiorly (i.e., downwardly as viewed in FIGS. 11 and 11A) from thecross member 57B. Both the cross member 57B and the extension 130 areprovided with a common dovetail slot 132. The extension 130 is anintegral unitary part of the cross member 57B and, in cross section, hasa generally semicircular cross sectional configuration with the sidefacing the patellar femoral flange piece 41B having a pair of flat faceson opposite sides of the dovetail slot 132.

The patellar femoral flange piece 41B, has a configuration similar tothat of the patellar femoral flange piece 41 as shown in FIG. 5,including a central wall surface 65B extending from a patellar engagingsurface 43B, a ledge 66B and a central engagement surface 67B. A boneengaging surface 68B extends from the central engagement surface 67Btoward the anterior end 45B. Extending superiorly from the bone engagingsurface 68B is an extension 134 having a dovetail 136 sized to be snuglyreceived in the dovetail slot 132 of the extension 130 with conformingmating surfaces. The dovetail 136 and dovetail slot 132 could have othercrossectional configurations from that shown in FIGS. 11, 11A and 11Bsuch as circular or rectangular. As will be appreciated and as can beseen from FIGS. 11A and 11B, the dovetail 136 is an integral unitarypart of the extension 134; however, it extends outwardly from thesurface 67B and upwardly from the surface 68B to join with surface 66B.

The respective extensions 130 of the condylar piece 42B and 134 of thepatellar femoral flange piece 41B, when joined together with thedovetail 136 positioned in the dovetail slot 132 will cooperate todefine a substantially cylindrical configuration; however, if desired, adifferent configuration, such as square, rectangular or rounded, couldbe utilized.

Preparatory to implantation of the condylar member 42B and patellarfemoral flange piece 41B, an aperture is drilled or otherwise formed inthe femur of sufficient size to receive the extensions 130 and 134.

Following positioning of the condylar piece 42B in the prepared femurwith its extension 130 positioned in the prepared bone cavity, thepatellar femoral flange piece 41B is moved therein, the dovetail 136 isaligned with the dovetail slot 132 and the patellar femoral flange piece41B is moved toward the prepared femur with the dovetail 136 slidingthrough the dovetail slot 132 until the surface 66B of the patellarfemoral flange piece 41B contacts the anterior surface of cross member578. Desirably, bone cement will be positioned in the prepared apertureof the femur to engage the adjoined extensions 130 and 134.

Referring to FIGS. 12 and 13, there is shown an embodiment of atwo-piece femoral component 74 with a first piece 75 of a patellarflange area having a patella engagement surface 76 and a second piece 77having a medial condyle portion 78 and a lateral condyle portion 79formed as an integral unitary piece. The second piece 77 has a series offlats 96, 97, 98, 99 for engagement with a prepared distal end of afemur.

The first piece 75 has an abutment wall 81 extending from the patellaengagement surface 76 and positioned to engage a corresponding abutmentwall 82 of the second piece 77. The line of juncture between theabutment wall 81 of the first piece 75 and the abutment wall 82 of thesecond piece 77 is in the area of low patella/femoral contact which is alow stress area of the femur. The abutment wall 81 extends onlypartially through the thickness of the first piece 75. The abutment wall81 joins with a second wall 83 disposed substantially at right anglesthereto (See FIG. 13). The second wall 83 extends to an end wall 84.Extending outwardly from the end wall 84 toward the plane defined by theabutment wall 81 is a ledge 85 having an upper surface 86 with a tongueor dovetail 87 projecting upwardly therefrom. The tongue 87 and uppersurface 86 extend throughout the breadth of the first piece 75. Thetongue 87 is provided with a pair of reverse taper surfaces 88 whichflare outwardly from one another in a direction away from the uppersurface 86.

Extending outwardly from the abutment wall 82 of the second piece 77 isan insert ledge 90 having an upper surface for mating engagement withthe second wall 83 of the first piece 75. The lower portion of theinsert ledge 90 opposite the upper surface has formed therein a dovetailgroove 92 extending the full breadth of the second piece 77 and sized toreceive the tongue 87 of the first piece 75. As can be seen from FIG.13, when the first piece 75 and second piece 77 are joined together,there will remain a gap 93 between the end wall 84 of the first piece 75and the end of the insert ledge 90 of the second piece 77. In order toprevent the engaged first piece 75 and second piece 77 from movinglaterally relative to one another, there is provided a tapered pin 94which may be driven into the gap 93 to function as a wedge putting thetongue 87 into compression in the dovetail groove 92 formed in the lowersurface of the insert ledge 90.

Referring to FIGS. 14 and 15, there is provided another embodiment ofprosthesis 100 with a first piece 101 having both a patellar flange area102 and an integral, unitary lateral condyle portion 103. The prosthesis100 also has a second piece 104 which is a medial condyle piece. Thefirst piece 101 has a first abutment wall 105 extending generallylaterally and a second abutment wall 106 extending generallylongitudinally with a curved wall section 107 joining the first abutmentwall 105 and the second abutment wall 106. Protruding outwardly from thesecond abutment wall 106 is a projection 110 having sidewalls 111 (onlyone of which is shown) tapering inwardly toward one another as theyextend outwardly from the second abutment wall 106 and end walls 112tapering inwardly toward one another as they extend outwardly from thesecond abutment wall 106. The tapering sidewalls 111 and end walls 112are joined by an outer wall 113 substantially parallel with the secondabutment wall 106. The projection 110 is integral and unitary with theremainder of the first piece 101 and may be formed by a milling process,for example. A threaded aperture 114 extends through the projection 110from the outer wall 113 and, preferably, extends into the adjacentportion of the first piece 101.

The second piece 104 has a first abutment wall 115 positioned to engagethe first abutment wall 105 of the first piece 101, a second abutmentwall 116 positioned and sized to engage the second abutment wall 106 ofthe first piece 101 and a curved wall 117 for engagement with the curvedwall 107 of the first piece 101. Formed in the second wall 116 is arecess 118 contoured to snuggly receive the projection 110 of the firstpiece 101. A laterally extending passageway 108 extends through thesecond piece 104 in alignment with the threaded aperture 114 of thefirst piece 101 when the second piece 104 is engaged thereto.

In order to join the second piece 104 to the first piece 101 there isprovided an elongated screw 120 having a threaded section 121 for matingwith the threads of the threaded aperture 114 of the first piece 101.The screw 120 has a cylindrical section 122 of larger diameter than thethreaded section 121 and sized to be snugly received in the passageway108 of the second piece. The screw 120 has an enlarged head 123 sized tofit in a countersunk area of the passageway 108 at the outer edge of thesecond piece 104.

Referring to FIGS. 16 and 17, there is shown a two-piece femoralcomponent 140 including a first piece 141 having both a lateral condyle142 and a medial condyle 143 formed as part of an integral, unitarypiece. The second piece 144 defines a patellar flange area of thefemoral component 140. The second piece 144 has a contoured abutmentwall 145 including a first flat surface 145A extending inwardly from thelateral side, a second flat surface 145B extending inwardly from themedial side of the second piece 144 and a recess defined by first andsecond side walls 145C and a bottom wall 145D. The sidewalls 145C taperinwardly toward one another as they extend from their respective flatsurfaces 145A and 145B to the bottom 145D. Preferably, the bottom wall145D is curved; however, it could be flat.

The first piece 141 is provided with an abutment wall 146 having acontour to be snuggly engaged to the abutment wall 145 of the secondpiece 144. As such, the abutment wall 146 includes a tongue 147contoured to fit snuggly in the groove defined by sidewalls 145C andbottom wall 145D of the second piece 144. The tongue 147 is defined bysidewalls 146C, 146C and an end wall 146D contoured to snuggly engagedthe wall 145D forming the bottom of the groove of the second piece 144.The walls 146C, 146C taper inwardly toward one another as they extendtoward the wall 146D and snuggly engage the tapered sidewalls 145C ofthe second piece 144.

The second piece 144 has formed therein a first passageway 148A whichextends inwardly from the lateral edge and is substantially parallel tothe first flat surface 145A and a second passageway 148B which extendsinwardly from the medial edge and is substantially parallel to thesecond flat surface 145B. A passageway 149 is formed in the tongue 147in a position to be aligned with the passageways 148A and 148B when thefirst piece 141 is engaged to the second piece 144, with the tongue 147fitting in the groove. A pin 150 may be inserted through the passageway148B, the passageway 149 and the passageway 148A to secure the firstpiece 141 to the second piece 144. The pin 150 could be cylindrical andpress fit into the respective passageways 148A, 148B and 149 assumingthe passageways were cylindrical or could be tapered assuming suchpassageways had the appropriate taper. Additionally, one of thepassageways, passageway 148A, for example, could be threaded, in whichcase the pin 150 would have a threaded end for engagement therewith.

In each of the embodiments, the respective lines of juncture betweenabutting walls of the assembled pieces have been selected to be locatedgenerally in the area of the normal femoral tidemark which is a lowstress area.

Referring now to FIG. 18, there is shown a tibial component generallydesignated by the numeral 161. The tibial component 161 includes atibial base 162 and a tibial stem 163. The tibial base 162 has aninferior surface 164 intended to engage the prepared proximal end of thetibia of the patient and a superior surface (not shown) to which may beaffixed a plastic insert contoured to be engaged by the condylarportions of a femoral component. The plastic insert may have one of anumber of well known mechanisms for being attached to the tibial base162 such as a dove tail locking mechanism, for example. The plasticinsert may be inserted either laterally or proximally depending on thespecific design of the tibial base and the condition of the patient asdetermined by the surgeon. Extending distally from the inferior surface164 is a base extension 165 having a generally cylindrical shape butwith a pair of fixation wings or fins 166 extending outwardly from thecylindrical portion of the base extension 165. A platform 167 is raisedfrom the inferior surface 164 and follows a contour encircling the baseextension 165 including the wings 166. The wings 166 function asfixation fins for maintaining the tibial base 162 in a fixed rotationalposition when implanted on the prepared proximal end of the tibia. Thetibial base 162 is provided with a notch 168 to accommodate theposterior cruciate ligament and a plurality of apertures 169 forreceiving screws for engagement to an augmentation block, if one isneeded, or for securing the tibial base 162 to the proximal end of aprepared tibia.

The tibial base 162 has a central passageway 170 extending from thesuperior surface 164 and through the cylindrical portion of the baseextension 165. That portion of the central passageway 170 in the baseextension 165 has wall surface which flares outwardly frusto conicallyand defines a Morse taper cavity 295 as it approaches the end of thebase extension 165. A recess defining a notch 240 is formed in the endof the base extension 165. That portion of the passageway adjacent thesuperior surface has a diameter sized to receive a screw 158 and acountersunk area 297 to receive the enlarged head of such screw 158.

The tibial stem 163 is provided with a pair of wings or fixation fins171 which, when the tibial stem 163 is engaged to the extension 165,will be aligned with and forming extensions of the respective wings orfins 166 of the tibial base 162. The tibial stem 163 is provided with aMorse taper extension 298 sized to be snugly received in the Morse tapercavity 295 of the tibial base 162. A shoulder 262 extends outwardly fromthe Morse taper extension 298. A raised tab 242 extends proximally fromthe shoulder 202 and is sized to fit snugly in the notch 210 and, whenso positioned, assures alignment of the fixation fins 171 of the tibialstem 163 with the fins 166 of the tibial base 162.

A threaded passageway 172 is formed in the Morse taper extension 298 andis aligned with the central passageway 170 when the tibial stem 163 isengaged to the extension 165. The tibial stem 163 is supported on thetibial base 162 by the screw 158 extending through the centralpassageway 170 of the tibial base 162 and engaged to the threadedpassageway 172. A plug 244 is engaged in the distal end of the tibialstem 163 to prevent blood or other contaminates from entering thethreaded passageway 172. The plug 244 may be secured to the tibial stem163 by means of a threaded extension engaging the threaded passageway172.

FIG. 18A shows an embodiment similar to FIG. 18 but in which there isprovided a stem extension 250 but not a plug such as the plug 244 ofFIG. 18. The stem extension 250 is provided with a Morse taper 252 atits proximal end 253. A threaded recess 254 extends distally from theproximal end and has a size smaller than the threaded passageway 172. Athreaded screw 258 sized to engage the threaded recess 254 secures thestem extension 250 and the tibial stem 163 to the tibial base 162. Thethreaded screw 258 is small enough to pass through the threadedpassageway 172 without engaging its threads.

The distal end of the tibial stem 163 has a cavity 260 taperingoutwardly in a distal direction and defining a Morse taper sized tosnuggly receive the Morse taper 252 of the stem extension 250. Twogrooves 270 are formed in the tibial stem 163, on opposite sides,distally spaced from the shoulder 262. The purpose of the grooves 270 isto permit engagement and support for the tibial stem during implantationas will be discussed hereinafter.

Referring to FIG. 19, there is a shown in section a modified embodimentof tibial component 200. Under this embodiment there is provided atibial base 202, a tibial stem 204 and a plastic insert 206 forengagement with the tibial base 202. The tibial base, as shown in FIG.19, has a raised wall 208 and a flat superior surface 210. The tibialbase 202 has an inferior surface 212 intended to engage the preparedproximal end of the tibia of the patient. A centrally positioned shortextension 213 extends from the inferior surface 212.

Extending through the tibial base 202 including the extension 213 is apassageway 214. That portion of the passageway 214 adjacent the inferiorsurface 210 is enlarged from the remainder of the passageway and isprovided with inwardly facing threads 215 in the area adjacent theinferior surface 210. That portion of the passageway 214 extending awayfrom the threads 215 is tapered to define a Morse taper cavity 216throughout the remainder of the thickness of the tibial base 202including the stem 213.

The tibial stem 204 is provided with an enlarged threaded flange 220sized to engage the threads 215 of the tibial base 202. Extending fromthe flange 220 is a Morse taper extension 222 sized and contoured to besnuggly received in the Morse taper cavity 216. Extending inwardly fromthe inferior surface 210 is a cavity defined by a series of flats 224which cooperate to define a hexagon or other conveniently shaped cavityfor receipt of a tool for engagement therein for threading the threadedflange 220 into the threads 215.

Extending from the cavity defined by the flats 224 is a threadedaperture 225. Extending distally from the Morse taper extension 222 is areduced size cylindrical extension 227.

The plastic insert 206 has molded therein a metal insert 230 having anenlarged flange 232 to ensure its firm engagement to the insert 206. Theinsert 206 is provided with a passageway 234 sized to receive a screw236 including its enlarged head 238. The metal insert 230 is providedwith a passageway 240 sized to receive the threaded portion of the screw236 but smaller than the enlarged head 238. Following engagement of thetibial stem 204 to the tibial base 202, the plastic insert 206 ispositioned on the inferior surface 210 within the upwardly extendingwall 208. The screw 236 is then engaged to the threaded aperture 225 tosecure the plastic insert 206 thereto.

In the surgical procedure for implanting the tibial component 200, theproximal end of the tibia is prepared by cutting a flat surface toreceive the inferior surface 212 of the tibial base 202 and a cavity isdrilled in the intramedullary canal of the tibia to receive the stem204. The tibial base 202 is positioned on the prepared flat surface withthe extension 213 positioned in the cavity. The tibial stem 204 is thenpositioned in the passageway 214 with the cylindrical extension 227passing through the Morse taper cavity 216 and into the cavity of theintramedullary canal. Using a tool engaged to the flats 224, the stem isthreadedly engaged to the threads 215 and the base 202 to cause theMorse taper extension 222 to firmly engage the Morse taper cavity 216.As may be seen in FIG. 19, the tibial stem 204 is so contoured relativeto the tibial base 202, that a gap 229 will remain between the distalside of the flange 220 and the surface of the tibial base 202 extendingradially outwardly from the Morse taper cavity 216. This ensures thatthe Morse taper extension 222 will firmly engage the Morse taper cavity216 upon threaded engagement of the threaded flange 220 to the threads215.

Referring now to FIGS. 20 and 21, there is shown another embodiment oftibial component 180 along with a tool 195 for use in implanting suchtibial component in the proximal end of a prepared tibia T. The tibialcomponent 180 includes a tibial base 181, a tibial stem 182 and aplastic insert 179 engaged to the tibial base 181. The tibial base 181has an inferior surface 183 intended to engage the prepared proximal endof the tibia T and a superior surface 184 to which may be affixed aplastic insert 179 contoured to be engaged by a femoral component. Thetibial base 181 has raised areas 185 along the anterior and posterioredges. Each of the raised areas is provided with an undercut wallsurface 186 defining grooves for receiving and retaining the plasticinsert 179.

Extending distally from the inferior surface 183 is an extension 187.The tibial base 181 has a central passageway 188 extending from thesuperior surface 184 and through the extension 187. The extension 187and the passageway 188 may be disposed at an angle of up to 10° relativeto a line perpendicular to the superior surface 184 in order toaccommodate the anatomy of the patient.

The tibial stem 182 is provided with a recess 190 sized and positionedto become an extension of the passageway 188 of the tibial base 181. Therecess 190 may be threaded for engagement by a threaded screw 196extending through the plastic insert 179 and its articular surface andthrough the passageway 188 to join the tibial stem 182 to the tibialbase 181. As shown in FIG. 21, the distal end 188A of the passageway 188may be tapered to define a Morse taper cavity. The tibial stem 182 isalso provided, at its proximal end, with a Morse taper extension 197sized to snugly engage the Morse taper cavity at the distal end 188A ofthe passageway 188. The tibial stem 182 is also provided with aplurality of outwardly facing grooves 189 to assist in fixation.

In preparing the proximal end of the tibia T to receive the tibialcomponent 180, the proximal end T1 of the tibia is cut to formsubstantially a flat surface. A cavity T2 is formed to receive thetibial stem 182. Since the cavity T2 may be oversized, the tibial stem182 is provided with an annular groove 198 sized to receive the tines195A of the tool 195. As can be seen in FIG. 21, with the tines 195Aengaged in the groove 198, the tool 195 can support the tibial stem 182at the proper location relative to the prepared proximal end T1 of thetibia T until such time as the screw 196 is engaged in the threadedrecess 190 to support such tibial stem 182 on the tibial base 181.

In implanting the tibial stem 163 of the embodiment of FIGS. 18 and 18A,a tool similar to the tool 195 may be used to engage the grooves 270 tosupport the stem 163 until it is engaged by the screw 158 or 258.

In each of the embodiments of FIGS. 18, 18A, 19, 20 and 21, it ispreferred that the surface of the tibial base which is to be contactedby a plastic insert be polished to a high degree, on the order of four(4) rms or less, to prevent premature wear on the surface of the plasticinsert engaged to the tibial base.

Description of Surgical Procedure

A medial parapatellar incision is made from the superior pole of thepatella to the tibial tuberosity. Medial parapatellar arthrotomy is madefrom the inferior edge of the vastus medial is to the tibial tuberosity.A subvastus or mid vastus arthrotomy may be utilized, based upon patientanatomy or surgeon experience.

The knee is place in extension and the patella excised without eversion,using a patellar clamp inserted into the prepatellar bursa, to preventdamage to the anterior skin.

An extramedullary tibial alignment guide is placed along the medial orlateral half of the tibia and secured with fixation pins. Anextrameduallary alignment guide of the type disclosed in applicationSer. No. 09/973,584 filed Oct. 9, 2001, assigned to the assignee of thepresent invention and incorporated herein by reference, is fixed to thefemur after performing the extramedullary alignment procedure, and thedistal femoral cut is made at the appropriate depth and angle of theimplant, nominally 6° valgus and 10-12 mm depth of cut. As analternative, an intramedullar alignment guide system could be used. Thiscut is taken all the way across both distal femoral condyles, ratherthan being unicondylar in nature. This cut is made at 90° to the femoralshaft.

The tibial component is implanted first. The fixation surface is coatedwith cement, and the modular tibial stem is driven through the reverseMorse taper to lock the tibial stem to the bone.

The anterior flange component is then implanted, followed by the lateralthen medial condyles. Once all pieces are loosely assembled inside theknee and proper alignment is assured, the locking pin is inserted fromthe side and rigidly fixes the components together. Final impaction isthen accomplished.

Lastly, the patella is cemented in place.

After all cement has hardened and excess is removed, the final polyslides in from the side, and is secured with an AP locking clip orscrew, which also helps lock the modular stem in place.

Routine closure is performed, and rapid rehab program initiated.

The above detailed description of the present invention is given forexplanatory purposes. It will be apparent to those skilled in the artthat numerous changes and modifications can be made without departingfrom the scope of the invention.

1-28. (canceled)
 29. A tibial component for use in knee arthroplastycomprising (a) a tibial base having (i) an inferior surface forengagement with a prepared surface at the proximal end of a tibia and(ii) a passageway extending through said base; (b) a tibial stemextending distally from said base; and (c) means for engaging said stemto said base.
 30. The tibial component of claim 29 wherein saidpassageway in the area of said tibial stem has a wall surface portiondefining a Morse taper and said tibial stem has a portion defining aMorse taper sized to be snugly engaged in said passageway Morse taperportion.
 31. The tibial component of claim 30 wherein a threadedaperture is provided in said tibial stem proximal end portion andfurther including a screw extending through said tibial base passagewayengaged to said threaded aperture.
 32. The tibial component of claim 30wherein said passageway Morse taper portion tapers outwardly in a distaldirection.
 33. The tibial component of claim 32 wherein a threadedaperture is provided in said tibial stem proximal end portion andfurther including a screw extending through said tibial base passagewayengaged to said threaded aperture.
 34. The tibial component of claim 32wherein said tibial stem is provided with an outwardly facing annulargroove spaced distally from said Morse taper portion.
 35. The tibialcomponent of claim 30 wherein said passageway Morse taper portion tapersinwardly in a distal direction.
 36. The tibial component of claim 35wherein a threaded aperture is provided in said tibial stem proximal endportion and further including a screw extending through said tibial basepassageway engaged to said threaded aperture.
 37. The tibial componentof claim 35 wherein said tibial base passageway is enlarged proximallyof said Morse taper portion to define a shoulder extending outwardlyfrom said Morse taper portion and further including inwardly facingthreads proximally of said shoulder.
 38. The tibial component of claim37 wherein said tibial stem has a flange portion proximally of said stemMorse taper portion and outwardly facing threads engaged to saidinwardly facing threads.
 39. The tibial component of claim 38 whereinsaid flange portion is spaced from said shoulder when said stem Morsetaper portion is snugly engaged to said base Morse taper portion. 40.The tibial component of claim 29 further including alignment means onsaid tibial base alignment with alignment means on said tibial stem. 41.A tibial component for a knee prosthesis comprising (a) a tibial basehaving an inferior surface for engaging prepared bone at the proximalend of the tibia, an extension extending distally from said inferiorsurface to a distal end, a passageway extending through said tibialbase, including through said extension, the distal end of saidpassageway defining a Morse taper; (b) a tibial stem extending from aproximal end to a distal end, said proximal end defining a Morse taperreceivable in said passageway Morse taper.
 42. The tibial componentaccording to claim 41 wherein said tibial stem has a recess extendingfrom said proximal end toward said distal end, said recess havingthreads or other retention means formed therein and further including anengagement member extending through said tibial base passageway andengaged to said threads or other retention means.
 43. The tibialcomponent of claim 41 wherein said passageway Morse taper portion tapersoutwardly in a distal direction.
 44. The tibial component of claim 43wherein a threaded aperture is provided in said tibial stem proximal endportion and further including a screw extending through said tibial basepassageway engaged to said threaded aperture.
 45. The tibial componentof claim 44 wherein said tibial stem is provided with an outwardlyfacing annular groove spaced distally from said Morse taper portion. 46.The tibial component of claim 41 wherein said passageway Morse taperportion tapers inwardly in a distal direction.
 47. The tibial componentof claim 46 wherein a threaded aperture is provided in said tibial stemproximal end portion and further including a screw extending throughsaid tibial base passageway engaged to said threaded aperture.
 48. Thetibial component of claim 46 wherein said tibial base passageway isenlarged proximally of said Morse taper portion to define a shoulderextending outwardly from said Morse taper portion and further includinginwardly facing threads proximally of said shoulder.
 49. The tibialcomponent of claim 48 wherein said tibial stem has a flange portionproximally of said stem Morse taper portion and outwardly facing threadsengaged to said inwardly facing threads.
 50. The tibial component ofclaim 49 wherein said flange portion is spaced from said shoulder whensaid stem Morse taper portion is snugly engaged to said base Morse taperportion.
 51. The tibial component of claim 41 further includingalignment means on said tibial base alignable with alignment means onsaid tibial stem. 52-62. (canceled)